Feature Article

Yet Another SDN Strategy To Migrate 2.5 to LTE

It’s been my pleasure to reconnect with Diana Cioniou and David Burgess from the YATE (Yet Another Telephony Engine) development team. YATE is GPL licensed, and is written in C++, with a modular design that can be extended using scripting languages like Perl, Python or PHP. Their latest exploit is YateBTS 5.0 which enables 2.5G services to upgrade to LTE.

With Legba and SS7Ware collaborating to release it into the open source community, YateBTS 5.0 allows a GSM/GPRS network implementation to bring IoT coverage with minimal cost. YateBTS 5.0 is available for download at www.yatebts.com.

I asked David Burgess some questions to expand on their press release about using YateBTS for Smart Farming. Here are his answers:

Carl Ford: Yate is a name many of us are familiar with. Are you built on the same base code? Or is it a matter of the same principles?

David Burgess: Our line of mobile equipment is based on Yate. This allows us to focus on developing a new technology while having the maturity of a largely deployed platform, to build a complete new technology. So we had all the bells and whistles like monitoring and flexible configuration and Web interfaces.

CF: So elaborate on what Yate is for my readers who are clueless.

DB: Yate is a "telephony engine," an engine for building telecom applications, just like you might have a "game engine" for games or an "app engine" for smartphone apps. Yate also includes a lot of pre-made modules that provide commonly needed services and support for a long list of telecom protocols.

Yate has been deployed for over ten years for lots of applications, including HLRs, CAMEL servers, switches and several kinds of signaling gateways. Some of the world's largest SIP networks are based on Yate.

All of the components of our mobile network (YateBTS, YateUCN, YateHSS/HLR, YateENB) are built using this Yate engine, leveraging the engine's power and the existing protocol modules. This approach also gives us a unified platform for network management, since everything is made of the same stuff. This approach also allows us to make software-only upgrades from GSM to LTE, and eventually to run GSM and LTE at the same time from the same radio.

CF: Is your solution specifically for GSM carriers?

DB: It is for GSM carriers, for LTE carriers, and for GSM carriers who plan to upgrade to LTE, either partially or totally. The YateUCN core network server can work with YateBTS for GSM/GPRS or with any eNodeB for LTE, or with both at the same time.

Our ability to support mixed GSM/LTE networks is one of the things that makes us special.

For example, we make it possible to deploy a GSM/GPRS network now and then upgrade to LTE on a site-by-site basis, without having to build a new core network. We also make it possible for an LTE operator to deploy a GSM/GPRS network that integrates into their 4G core network, much more simply than solutions from other vendors. This is important because GPRS is a better match than LTE for most IoT applications, especially in rural areas. And, of course, GSM will continue to be an excellent technology for basic telephone service in many areas for several more years.

CF: You have mentioned that carriers supporting rural areas find this attractive. What makes that story more compelling than for urban areas? Is it the lack of shared resources?

DB: Serving rural areas is a difficult task just because the cost to install a network in rural is higher than in urban areas and the revenue is the same. SatSite and YateUCN bring down the CAPEX and OPEX of the network to the point where it becomes profitable to run a network in almost the entire USA.

Rural requires more resources than urban from the carriers, due to low population density. But IoT can change that, because in the rural areas you will have a larger number of devices per user than in the urban areas. You will have most of the same applications found in urban areas, plus rural-specific applications on top of that, like smart farming (interconnected automated farming equipment) and long-haul transportation.

IoT creates an interesting market but it needs to have the right technical and financial solution to serve it. So having a feasible solution and extra users changes the equation for the carriers in the rural areas.

CF: In the U.S. we have small rural carriers, while in Europe the history has been national carriers that are now privatized. Are there specific markets that are best suited to be your customers?

DB: The market is changing even in Europe with the allocation of new spectrum for LTE. But the planet is our playground and we would like to rather serve the unserved three billion and also to bring more connectivity to the already served ones. We are presently focused on small projects. These mostly come from small operators. But there are good fits for our technology in many places and with many operators, including in Europe.

CF: Voice over LTE has been implemented in the U.S. at the core of the network and the VoLTE client is directly connected to the core. Do you handle VoLTE the same way?

DB: VoLTE is a very nice technology, very wrongly understood. We've been in the SIP (protocol behind VoLTE) market for about 10 years, so our approach was simple and mature from the beginning.

We have to work with the UE client as it exists, so the protocol is the same. The big difference is a greatly simplified implementation, with just one box providing all of the EPC and IMS functions, including VoLTE. Another difference is that the Yate implementation of VoLTE uses back-to-back user agents, not SIP proxies. That is important for security, because it prevents a buggy or malicious VoLTE client from sending malformed messages directly to other clients.